Cutis

The Diagnosis: Collision Tumor

Excisional biopsy and histopathological examination demonstrated a collision tumor composed of a benign intradermal melanocytic nevus, tumor of follicular infundibulum, and an underlying sclerosing epithelial neoplasm, with a differential diagnosis of desmoplastic trichoepithelioma, morpheaform basal cell carcinoma, and microcystic adnexal carcinoma (Figure).

Common acquired melanocytic nevus presents clinically as a macule, papule, or nodule with smooth regular borders. The pigmented variant displays an evenly distributed pigment on the lesion. Intradermal melanocytic nevus often presents as a flesh-colored nodule, as in our case. Histopathologically, benign intradermal nevus typically is composed of a proliferation of melanocytes that exhibit dispersion as they go deeper in the dermis and maturation that manifests as melanocytes becoming smaller and more spindled in the deeper portions of the lesion.¹ These 2 characteristics plus the bland cytology seen in the present case confirm the benign characteristic of this lesion (Figure, B).

In addition to the benign intradermal melanocytic nevus, an adjacent tumor of follicular infundibulum was noted. Tumor of follicular infundibulum is a rare adnexal tumor. It occurs frequently on the head and neck and shows some female predominance.^2,3 Multiple lesions and eruptive lesions are rare forms that also have been reported.⁴ Histopathologically, the tumor demonstrates an epithelial plate that is present in the papillary dermis and is connected to the epidermis at multiple points with attachment to the follicular outer root sheath. Peripheral palisading is characteristically present above an eosinophilic basement membrane (Figure, A). Rare reports have documented sebaceous and eccrine differentiation.^5,6

Tumor of follicular infundibulum has been reported to be associated with other tumors. Organoid nevus (nevus sebaceous), trichilemmal tumor, and fibroma have been reported to occur as a collision tumor with tumor of follicular infundibulum. An association with Cowden disease also has been described.⁷ Biopsies that represent partial samples should be interpreted cautiously, as step sections can reveal basal cell carcinoma.

The term sclerosing epithelial neoplasm describes tumors that share a paisley tielike epithelial pattern and sclerotic stroma. Small specimens often require clinicopathologic correlation (Figure, C). The differential diagnosis includes morpheaform basal cell carcinoma, desmoplastic trichoepithelioma, and microcystic adnexal carcinoma. A panel of stains using Ber-EP4, PHLDA1, cytokeratin 15, and cytokeratin 19 has been proposed to help differentiate these entities.⁸ CD34 and cytokeratin 20 also have been used with varying success in small specimens.^9,10

The Diagnosis: Collision Tumor

Excisional biopsy and histopathological examination demonstrated a collision tumor composed of a benign intradermal melanocytic nevus, tumor of follicular infundibulum, and an underlying sclerosing epithelial neoplasm, with a differential diagnosis of desmoplastic trichoepithelioma, morpheaform basal cell carcinoma, and microcystic adnexal carcinoma (Figure).

Common acquired melanocytic nevus presents clinically as a macule, papule, or nodule with smooth regular borders. The pigmented variant displays an evenly distributed pigment on the lesion. Intradermal melanocytic nevus often presents as a flesh-colored nodule, as in our case. Histopathologically, benign intradermal nevus typically is composed of a proliferation of melanocytes that exhibit dispersion as they go deeper in the dermis and maturation that manifests as melanocytes becoming smaller and more spindled in the deeper portions of the lesion.¹ These 2 characteristics plus the bland cytology seen in the present case confirm the benign characteristic of this lesion (Figure, B).

In addition to the benign intradermal melanocytic nevus, an adjacent tumor of follicular infundibulum was noted. Tumor of follicular infundibulum is a rare adnexal tumor. It occurs frequently on the head and neck and shows some female predominance.^2,3 Multiple lesions and eruptive lesions are rare forms that also have been reported.⁴ Histopathologically, the tumor demonstrates an epithelial plate that is present in the papillary dermis and is connected to the epidermis at multiple points with attachment to the follicular outer root sheath. Peripheral palisading is characteristically present above an eosinophilic basement membrane (Figure, A). Rare reports have documented sebaceous and eccrine differentiation.^5,6

Tumor of follicular infundibulum has been reported to be associated with other tumors. Organoid nevus (nevus sebaceous), trichilemmal tumor, and fibroma have been reported to occur as a collision tumor with tumor of follicular infundibulum. An association with Cowden disease also has been described.⁷ Biopsies that represent partial samples should be interpreted cautiously, as step sections can reveal basal cell carcinoma.

The term sclerosing epithelial neoplasm describes tumors that share a paisley tielike epithelial pattern and sclerotic stroma. Small specimens often require clinicopathologic correlation (Figure, C). The differential diagnosis includes morpheaform basal cell carcinoma, desmoplastic trichoepithelioma, and microcystic adnexal carcinoma. A panel of stains using Ber-EP4, PHLDA1, cytokeratin 15, and cytokeratin 19 has been proposed to help differentiate these entities.⁸ CD34 and cytokeratin 20 also have been used with varying success in small specimens.^9,10

The Diagnosis: Collision Tumor

Excisional biopsy and histopathological examination demonstrated a collision tumor composed of a benign intradermal melanocytic nevus, tumor of follicular infundibulum, and an underlying sclerosing epithelial neoplasm, with a differential diagnosis of desmoplastic trichoepithelioma, morpheaform basal cell carcinoma, and microcystic adnexal carcinoma (Figure).

Common acquired melanocytic nevus presents clinically as a macule, papule, or nodule with smooth regular borders. The pigmented variant displays an evenly distributed pigment on the lesion. Intradermal melanocytic nevus often presents as a flesh-colored nodule, as in our case. Histopathologically, benign intradermal nevus typically is composed of a proliferation of melanocytes that exhibit dispersion as they go deeper in the dermis and maturation that manifests as melanocytes becoming smaller and more spindled in the deeper portions of the lesion.¹ These 2 characteristics plus the bland cytology seen in the present case confirm the benign characteristic of this lesion (Figure, B).

In addition to the benign intradermal melanocytic nevus, an adjacent tumor of follicular infundibulum was noted. Tumor of follicular infundibulum is a rare adnexal tumor. It occurs frequently on the head and neck and shows some female predominance.^2,3 Multiple lesions and eruptive lesions are rare forms that also have been reported.⁴ Histopathologically, the tumor demonstrates an epithelial plate that is present in the papillary dermis and is connected to the epidermis at multiple points with attachment to the follicular outer root sheath. Peripheral palisading is characteristically present above an eosinophilic basement membrane (Figure, A). Rare reports have documented sebaceous and eccrine differentiation.^5,6

Tumor of follicular infundibulum has been reported to be associated with other tumors. Organoid nevus (nevus sebaceous), trichilemmal tumor, and fibroma have been reported to occur as a collision tumor with tumor of follicular infundibulum. An association with Cowden disease also has been described.⁷ Biopsies that represent partial samples should be interpreted cautiously, as step sections can reveal basal cell carcinoma.

The term sclerosing epithelial neoplasm describes tumors that share a paisley tielike epithelial pattern and sclerotic stroma. Small specimens often require clinicopathologic correlation (Figure, C). The differential diagnosis includes morpheaform basal cell carcinoma, desmoplastic trichoepithelioma, and microcystic adnexal carcinoma. A panel of stains using Ber-EP4, PHLDA1, cytokeratin 15, and cytokeratin 19 has been proposed to help differentiate these entities.⁸ CD34 and cytokeratin 20 also have been used with varying success in small specimens.^9,10

The Diagnosis: PELVIS Syndrome

Infantile hemangiomas (IHs) are present in up to 10% of infants by 1 year of age and are most commonly located on the face and upper extremities. Less than 10% of IHs develop in the perineum.¹ Perineal IHs are benign tumors of the vascular endothelium that present as plaques and commonly are accompanied by painful ulcerations. Ulceration is more common in the diaper area secondary to irritation from urine, stool, and friction.² Although most IHs are benign isolated findings, facial IHs have been associated with several syndromes including Sturge-Weber and PHACE (posterior fossa brain malformations, hemangiomas, arterial anomalies, cardiac anomalies and coarctation of the aorta, and eye and endocrine abnormalities) syndromes.³ Researchers also have identified an association between lumbosacral IHs and spinal dysraphism (tethered spinal cord).⁴

A smaller number of studies have investigated congenital anomalies related to perineal IH,^1,5 specifically PELVIS syndrome. The acronym PELVIS has been used to describe a syndrome of congenital malformations including perineal hemangioma, external genital malformations, lipomyelomeningocele, vesicorenal abnormalities, imperforate anus, and skin tag.¹ An alternative description of similar findings is LUMBAR (lower body hemangioma and other cutaneous defects; urogenital anomalies, ulceration; myelopathy; bony deformities; anorectal malformations, arterial anomalies; and renal anomalies).⁵ Researchers have suggested that both of these acronyms describe the same syndrome, and it is common for the syndrome to be incomplete.⁶ One study (N=11) found that perineal hemangiomas are most commonly associated with anal malformations (8 patients), followed by urinary tract abnormalities (7 patients) and malformation of the external genitalia (7 patients). A skin tag was present in 5 patients.¹ The pathogenesis of PELVIS syndrome is unknown.

When an infant presents with a perineal hemangioma and physical examination suggests PELVIS syndrome, imaging should be performed to evaluate for other anomalies. Before 4 months of age, ultrasound should be utilized to investigate the presence of reno-genitourinary or spinal malformations. Magnetic resonance imaging is the preferred imaging modality in children older than 4 months.⁷ Management of PELVIS syndrome requires a multidisciplinary approach and early recognition of the full extent of congenital malformations. Pediatric dermatologists, urologists, endocrinologists, and neonatologists have a role in its diagnosis and treatment.

The Diagnosis: PELVIS Syndrome

Infantile hemangiomas (IHs) are present in up to 10% of infants by 1 year of age and are most commonly located on the face and upper extremities. Less than 10% of IHs develop in the perineum.¹ Perineal IHs are benign tumors of the vascular endothelium that present as plaques and commonly are accompanied by painful ulcerations. Ulceration is more common in the diaper area secondary to irritation from urine, stool, and friction.² Although most IHs are benign isolated findings, facial IHs have been associated with several syndromes including Sturge-Weber and PHACE (posterior fossa brain malformations, hemangiomas, arterial anomalies, cardiac anomalies and coarctation of the aorta, and eye and endocrine abnormalities) syndromes.³ Researchers also have identified an association between lumbosacral IHs and spinal dysraphism (tethered spinal cord).⁴

A smaller number of studies have investigated congenital anomalies related to perineal IH,^1,5 specifically PELVIS syndrome. The acronym PELVIS has been used to describe a syndrome of congenital malformations including perineal hemangioma, external genital malformations, lipomyelomeningocele, vesicorenal abnormalities, imperforate anus, and skin tag.¹ An alternative description of similar findings is LUMBAR (lower body hemangioma and other cutaneous defects; urogenital anomalies, ulceration; myelopathy; bony deformities; anorectal malformations, arterial anomalies; and renal anomalies).⁵ Researchers have suggested that both of these acronyms describe the same syndrome, and it is common for the syndrome to be incomplete.⁶ One study (N=11) found that perineal hemangiomas are most commonly associated with anal malformations (8 patients), followed by urinary tract abnormalities (7 patients) and malformation of the external genitalia (7 patients). A skin tag was present in 5 patients.¹ The pathogenesis of PELVIS syndrome is unknown.

When an infant presents with a perineal hemangioma and physical examination suggests PELVIS syndrome, imaging should be performed to evaluate for other anomalies. Before 4 months of age, ultrasound should be utilized to investigate the presence of reno-genitourinary or spinal malformations. Magnetic resonance imaging is the preferred imaging modality in children older than 4 months.⁷ Management of PELVIS syndrome requires a multidisciplinary approach and early recognition of the full extent of congenital malformations. Pediatric dermatologists, urologists, endocrinologists, and neonatologists have a role in its diagnosis and treatment.

The Diagnosis: PELVIS Syndrome

Infantile hemangiomas (IHs) are present in up to 10% of infants by 1 year of age and are most commonly located on the face and upper extremities. Less than 10% of IHs develop in the perineum.¹ Perineal IHs are benign tumors of the vascular endothelium that present as plaques and commonly are accompanied by painful ulcerations. Ulceration is more common in the diaper area secondary to irritation from urine, stool, and friction.² Although most IHs are benign isolated findings, facial IHs have been associated with several syndromes including Sturge-Weber and PHACE (posterior fossa brain malformations, hemangiomas, arterial anomalies, cardiac anomalies and coarctation of the aorta, and eye and endocrine abnormalities) syndromes.³ Researchers also have identified an association between lumbosacral IHs and spinal dysraphism (tethered spinal cord).⁴

A smaller number of studies have investigated congenital anomalies related to perineal IH,^1,5 specifically PELVIS syndrome. The acronym PELVIS has been used to describe a syndrome of congenital malformations including perineal hemangioma, external genital malformations, lipomyelomeningocele, vesicorenal abnormalities, imperforate anus, and skin tag.¹ An alternative description of similar findings is LUMBAR (lower body hemangioma and other cutaneous defects; urogenital anomalies, ulceration; myelopathy; bony deformities; anorectal malformations, arterial anomalies; and renal anomalies).⁵ Researchers have suggested that both of these acronyms describe the same syndrome, and it is common for the syndrome to be incomplete.⁶ One study (N=11) found that perineal hemangiomas are most commonly associated with anal malformations (8 patients), followed by urinary tract abnormalities (7 patients) and malformation of the external genitalia (7 patients). A skin tag was present in 5 patients.¹ The pathogenesis of PELVIS syndrome is unknown.

When an infant presents with a perineal hemangioma and physical examination suggests PELVIS syndrome, imaging should be performed to evaluate for other anomalies. Before 4 months of age, ultrasound should be utilized to investigate the presence of reno-genitourinary or spinal malformations. Magnetic resonance imaging is the preferred imaging modality in children older than 4 months.⁷ Management of PELVIS syndrome requires a multidisciplinary approach and early recognition of the full extent of congenital malformations. Pediatric dermatologists, urologists, endocrinologists, and neonatologists have a role in its diagnosis and treatment.